Loudspeaker arrangement



ug @9 E94@ H, ENECKE ET AL, ZDZQ?? LOUDSPEAKER ARRANGEMENT Filed NOV. le. 1933 INVENTORS HElA/R/CH BEA/ECKE LE /ALK ATTORNEY Patented Aug. 6, 1940 LOUDSPEAKER ARRANGEMENT l'Heinrich Benecke and Leo Bialk, Berlin, Germany, assignors to Telefunken Gesellschaft fr Drahtlose Telegraphie in. lo. Il., Berlin, Germany, a corporation of Germany Application November 16, 1938, Serial No. 240,650 In Germany November 1li, 1937 l Claim.

For outdoor entertainment and public address systems, and also for enclosed rooms or spaces, it is often desirable to have the loudspeaker mounted in some concealed place. According to the invention, arrangements are made so that the sound issues from underneath the licor or ground. The loudspeakers therefore are mounted below the floor or the ground. In order that the range or area supplied with sound may be larger in reference to the vertical axis, and in order that, in reference to the horizontal axis, the higher pitches may be reproduced with better quality, the axis of the loudspeaker to the horizontal line is preferably inclined at an acute angle. This plan moreover oiers the advantage that the loudspeakers Will not be impaired in their operation by rain and splashing water and are protected against the entry of foreign bodies. In the vicinity of the loudspeaker the bottom (ground) plank must be shut and protrude somewhat above the loudspeaker in order to prevent the entrance of dirt. At a little greater distance from the loudspeaker, a grating is provided, built so ruggedly that it will stand the Weight of a person standing thereon. Of course, this grating must also be so proportioned that the acoustic properties of the loudspeaker will not be influenced at all or only slightly. It will be understood that drain ducts to carry away rain and other water Will have to be provided.

In the appended drawing Figs. 1, 2 and 3 show exemplified embodiments of the present invention. Fitted into the ground is a box i in which is accommodated the loudspeaker 2. The loudspeaker divides the box into two parts, care having to be taken so that the sound waves issuing from the front of the diaphragm will not have a chance to communicate With the wave given off from the posterior face thereof. In order to avoid space resonances, it is recommendable to drape the space posteriorly of the diaphragm, as known in the art, with felt 3 or by packing it with cotton or the like. For carrying off rain water, a drain hole 4 is provided. The horn-like construction as shown oiers the advantage that the use of the device is made essentially independent of the acoustic properties of the posterior space, provided it is not of unduly limited dimensions. Owing to the fact that the loudspeaker is mounted in the enclosure a little distance away from the grating 5 part 6 of the top cover plate will protect the loudspeaker from soiling.

Instead of disposing the loudspeaker arrangement ilush with the ground as shown in the drawing, it is also possible to place such loudspeaker into enclosures or casings having a tortoise-like cover raised but slightly above the ground of the kind serving for traic regulation in the streets. The loudspeakers could also be set into bases which also are raised but little above the ground. This has the advantage that a listener cannot stand right on top of the speaker.

In the exemplified embodiment of Fig. 1, the loudspeaker is mounted so that its axis presents an inclination to the horizontal. It is, of course, also feasible to mount the loudspeaker so that its axis is parallel to the horizontal as shown in Fig. 2. The reference numerals in Fig. 2 correspond to those in Fig. 1. But the arrangement Fig. 2 comprises additional sound duct walls or baliies 'l the eil'ect of which is that the sound radiated 01T from the loudspeaker 2 issues at an acute angle.

Apart from the modes of mounting of loudspeakers shown in the drawing, recourse could be had also to other forms of mounting. For instance, the loudspeaker axis could present any other angle in reference to the horizontal, provided that care is taken so that the acoustic waves radiated from the loudspeaker are made to issue at an acute angle to the horizontal, and this is done in the embodiment Fig. 2, where the axis is parallel, by the aid of baiiles.

Another embodiment of this invention is to install a mushroom type loudspeaker, that is, a loudspeaker with non-directional characteristic into the ground as shown in Fig. 3. In the surface of the ground, for instance, in the lawn of a parade ground or else in the floor of a room, is an opening lll adapted to accommodate the non-directional loudspeaker i l. On. top the mouth of the loudspeaker is covered by the mushroom-shaped inserted part l2; the outlet i3 for the sound is shut by means of a cover if! of truncated-cone shape and having sound apertures. The mouth i3 itself is protected against the entrance of water, foreign bodies, etc., by means oi a screen i5. The loudspeaker system is indicated at i6, and the diaphragm at il.

From the loudspeaker i6, a flexible connectingk cable I8 is brought to the socket i@ which is preferably mounted iixed in the ground. A drain hole 2Q is provided here just as in Figs. l and 2.

As regards the arrangement of the drain holes in the embodiments Figs. 1 to 3 it is to be noted that it is recommendable to dispose the loudspeakers a few centimeters above these drain holes in order that the speaker may not be damaged by possibly occurring clogging of the drains.

What We claim is: A subterranean loudspeaker installation com- 5 prising a housing disposed underneath the surface that part having the outlet portion in the upper Wall andthe back of the diaphragm radiating sound Waves into the other part Which is completely enclosed, the latter part being lined With felt padding for absorbing the sound Waves from -the back of the diaphragm, and a plurality of upwardly curved spaced members serving as directional baille means extending between the front of the diaphragm and the outlet portion of thehousing for guiding the sound Waves radiJ 10 ated from the front of the diaphragm.

HEINRICH BENECKE. LEO BIALK. 

